Where:- F = length of pendulum in feet L = length of pendulum in inches N = number of oscillations per minute T = time of one oscillation G = gravity. Approx. 32.2 if working in feet, or 386.4 if in inches.
G = 32.088 ( 1+ 0.005133 Sin2? ) ( 1- 2H/R) Where ? =latitude H = height above sea level NOTE. L = 39.1383 " in the latitude of London for T = 1 second
STEAM /WATER HEATING..
For heating, Water tube boiler 65% to 82% efficient Lancashire boiler 60% to 80% efficient. Open house fire, 20 - 25% to room + 20 - 25% to walls etc. remainder lost.
Internal pressure in hot water cylinder or similar = surface area of cylinder (in sq. inches) x 0.434 per foot head of water. (result is in lbs.)
WIND MILLS. Normal dimension of windmill sails. Length 30 ft., Breadth of base = 12 inches, depth of base = 9 in., Breadth of tip = 6 in., depth of tip = 4 1/2".
Power of windmills. HP = 0.00000091 A x V3, Where:- A = Total area of sales in sq. ft., V = wind velocity in ft. per second.
Velocity of sail tips is roughly 2.6 x V.
Annular mills (often called American windmills, have fixed wooden or steel vanes arranged in an annulus. These were mainly used for raising water. The following table shows the power generated by this type of windmill.
Efficiency of Annular windmill working 8 hours per day pumping water (typical).
WATER MILLS.
Overshot wheel is suitable for falls from 10 ft to 70 ft. Efficiency is up to 65% or 70%. One guide to power is that 12 cu. ft. of water should give 1 HP / ft. of fall.
Breast shot wheel acts by weight only. Efficiency around 70% to 75%. With low-breast wheels, the buckets should be 1 to 1.5 ft apart.
Undershot wheel. With radial floats only about 33% efficient. With curved floats (Poncelet floats) , can be up to 65% efficient. Suitable for falls up to 6 ft., and diameter should be 4 x fall. Circumferential speed should be 3 to 6 ft / second.
( The main gear (properly called the pit wheel) is often fitted with teeth made from apple wood. After some years of use in a damp atmosphere the wood attains the hardness of, well, sufficient to blunt chisels! Oh, and apple wood is also excellent for turning, and makes a nice smell when burned. )
When grinding grain, the speed of the stone can vary from 250 rpm (3 ft. diam. stone) to 150 rpm (4 ft diam. Stone).
Apart from grinding corn ( the use which is usually first in most peoples minds) watermills were used for many purposes. Water powered bellows and hammers were much used in the iron industry. Hammers weighed up to about 1.5 tons, and small hammers (weight around 150 lbs.) Operated at up to 200 strokes per minute.
MANUAL POWER. A man can work for 8 hours per day and generate between 1/10 and 1/20 HP. But, on a treadmill he can produce over 1 HP.
MILES. (Old measures). Irish mile = 2240 yards. Scottish mile = 1984 yards. London mile = 1666.66 yards = 5000 feet. French mille = 2132 yards. Austrian mile = 8296 yards California legua = 2.6335 miles = 5000 varas. (Gee, I bet you wanted to know that.)
